Feeder for apparatus for ejecting urethane foam formed by the mixture of resin and isocyanate with flushing liquid

ABSTRACT

A feeder for apparatus for ejecting a mixture of liquids, e.g. urethane foam, comprises a pair of swash plate proportioning pumps one individual to each of the liquids, e.g. resin and isocyanate, each proportioning pump being fed by a gear pump from a supply of the respective liquid. Seepage along the drive shafts of the isocyanate pumps is continuously removed by bathing them in a recirculating stream of flushing agent. The swash plate and gear pumps and flushing agent pump are all driven by a single motor from a common chain drive. The liquids are heated during passage through separate hoses to a common dispensing head or gun, by immersed coil electric resistance heaters extending lengthwise freely within the hoses. A novel control system is provided for the hose heater circuit, the adequacy of the liquid supply and other operating conditions.

This is a division of application Ser. No. 727,981, filed Sept. 29, 1976now U.S. Pat. No. 4,131,395.

The present invention relates to a feeder for feeding a plurality ofliquids to apparatus for ejecting a mixture of the plurality of liquids.Apparatus to be fed by the feeder of the present invention can forexample be of the type disclosed and claimed in U.S. Pat. Nos.2,890,836, 3,263,928 and 3,876,145, the disclosure of which isincorporated herein by reference. It is to be emphasized, however, thatthe present invention is not an improvement on or an alternative to theclaimed subject matter of those patents, but rather is for use withapparatus such as the apparatus of those patents and with other suchapparatus for receiving a plurality of separate streams of liquid andfor mixing liquids together and ejecting a mixture of that plurality ofliquids.

Accordingly, it is an object of the present invention to provide afeeder for apparatus for ejecting a mixture of a plurality of liquids,with improved means to heat the liquids and to control the heating ofthe liquids.

Another object of the present invention is to provide such a feeder,which, when one of the liquids is an isocyanate component of apolyurethane system, has improved means for avoiding the undesirableeffects of the escape of isocyanate.

A further object of the present invention is the provision of such afeeder, which automatically guards against operation with an inadequatesupply of any fed liquid.

A still further object of the present invention is the provision of sucha feeder with improved controls responsive to the pressure of the fedliquids at a plurality of points in the system.

Still another object of the present invention is the provision of such afeeder with an improved drive means therefor.

Finally, it is an object of the present invention to provide such afeeder which will be relatively simple and inexpensive to manufacture,adjust, operate, maintain and repair, and rugged and durable in use.

Other objects, features and advantages of the present invention willbecome apparent from a consideration of the following description, takenin connection with the accompanying drawings, in which:

FIG. 1 is a schematic overall diagram of apparatus according to thepresent invention;

FIG. 2 is a schematic diagram of the fluid circuit for avoidingundesirable results arising from the escape of isocyanate in the case ofa urethane system;

FIG. 3 is a fragmentary cross-sectional view of a gear feed pump as usedin the invention, modified to control the escape of isocyanate;

FIG. 4 is a cross-sectional view of a swash plate proportioning pump asused in the present invention, modified for controlling the escape ofisocyanate;

FIG. 5 is a fragmentary view showing the circuit control responsive tothe angle of the swash plate of the proportioning pumps;

FIG. 6 is a bottom plan view of the machine showing the common drive ofthe moving parts;

FIG. 7 is a view partly in cross section and with parts broken away, ofthe hose heater system of the present invention; and

FIGS. 8A and 8B are each a circuit diagram of the feeder of the presentinvention.

OVERALL CONFIGURATION

Referring now to the drawings in greater detail, and first to FIG. 1, anembodiment of the present invention is illustrated which comprises afeeder for two mutually reactive liquids, namely, a urethane resin andan isocyanate hardener therefor, of conventional composition. The resinin liquid phase is contained in a supply container 1; while theisocyanate in liquid phase is contained in a supply container 3. Sourcesof nitrogen under pressure, at 5 and 7, respectively, protect the liquidagainst air and moisture and ensure that the liquids will leave theirrespective supply containers at a small positive pressure, for example 3psig or less. The use of nitrogen in this fashion, however, is entirelyconventional.

The mutually reactive liquids separately leave their respectivecontainers and pass through conduits 9 and 11, respectively, to machine13, to which conduits 9 and 11 are detachably interconnected byconventional couplings 15 and 17, respectively. Machine 13 comprises aframe on which are mounted the motor and pumps which, apart from thematerial supply containers and the hoses to the dispensing gun itself,constitute the principal portions of the invention, and to which thesupply containers and gun hoses are detachably interconnected by meansof flexible conduits.

Machine 13 thus may comprise a base plate on which are mounted variousprincipal components of the invention, and which may in turn be mountedon wheels for easy transportation. On machine 13, the resin supplyproceeds through conduit 19 and filter 21 to a resin feed pump 23 whichis a gear pump in which the pressure of the resin is raised from, forexample, 3 psi to, for example, 20 psi. A bypass 25 under control of aspring-urged pressure relief valve 27 limits the pressure in conduit 19downstream of pump 23. Bypass 25 is diagrammatically shown in FIG. 1 asa bypass conduit, but it will be understood that it can be merely abypass orifice within pump 23.

From feed pump 23, the resin passes to a positive displacementproportioning pump 29 which is adjustable to set the proportion ofresin-to-isocyanate within a range of, say, 1:3 to 3:1. A bypass conduit31 under control of a manually operated valve 33 permits resin inconduit 19 upstream of pump 29 to be selectively diverted through thecasing of pump 29 and thence through a return conduit 35 past detachablecoupling 37 and back to container 1.

Similarly, on the isocyanate side, the liquid proceeds from coupling 17through conduit 39 and filter 41, to isocyanate feed pump 43 with itsbypass 45 controlled by pressure relief valve 47. Bypass 45, like bypass25, can be merely a bypass orifice in pump 43.

Isocyanate from feed pump 43 at a pressure of, say, 25 psi, proceeds toproportioning pump 49 which, like pump 29, is a rotary cylinder multiplepiston type swash plate pump with a bypass conduit 51 under control of amanually operated valve 53 that returns liquid through the casing ofpump 49 to return conduit 55 and thence through detachable coupling 57to isocyanate container 3.

Feed pumps 23 and 43 thus maintain a base pressure, for example at leastabout 15 psig, upstream of the proportioning pumps 29 and 49.Pressure-actuated switches 59 and 61, in conduits 19 and 39,respectively, immediately upstream of pumps 29 and 49, respectively, areresponsive to a decrease in pressure to a value below this basepressure, which is indicative of low material supply, and which servesto control the machine in a manner to be described in greater detailhereinafter.

The resin and isocyanate, now under a pressure of, say, 800 psig, leavetheir respective proportioning pumps and leave machine 13 throughcouplings 63 and 65, respectively, and proceed through short lengths ofunheated hose 67 and 69 to couplings 71 and 73, whence they pass throughheated hoses 75 and 77 to conventional couplings 79 and 81 by which thehoses 75 and 77 are respectively secured to a conventional head 83 of aconventional gun 85. Gun 85 can be of the entirely conventional type inwhich a valving rod is reciprocated to open and close a mixing chamberfed by inlets for the various liquids, the valving rod beingreciprocated by an air piston whose air supply is under the control of atrigger valve 86.

Couplings 71 and 73 are in electrical circuit via conductors 87 and 89,with the secondary winding of an isolation transformer 91, in which theprimary voltage of, say, 220 volts is stepped down to 48 volts, thislatter then passing in series from one of the couplings 71 and 73through conductors that extend within the hoses 75 and 77 full lengththereof, through the couplings 79 and 81 and the head 83 of gun 85,thereby to heat the resin and isocyanate by means of an immersedelectrical resistance heater in a manner that will be described ingreater detail hereinafter.

FLUSH SYSTEM FOR ISOCYANATE PUMPS

In the case of a urethane system in which the isocyanate is separatelypumped to the gun, a problem arises with the pumps 43 and 49, which arerotary pumps driven by a shaft. Pump 43, a gear pump, has one driveshaft, which drives one of the gears, the other gear being a slave. Pump49, which is a swash plate pump, has a drive shaft which rotates thecylinder in which the plural pistons reciprocate parallel to the axis ofthe shaft. In each case, however, the drive shaft must be sealed in aneffort to prevent the escape of isocyanate along the drive shaft, as theisocyanate is hygroscopic and tends to thicken and gum in the presenceof atmospheric moisture, so that an isocyanate gum builds up on theshaft; and this damages the pump seals. Thus, a very serious problem inpumping isocyanate has been the problem of how to hold a seal whenisocyanate is pumped to high pressure.

It is known to bathe the drive shaft of a rotary pump used in connectionwith isocyanate, with a diluent for the isocyanate. But according to thepresent invention, the diluent is pumped in a closed circuit, to bathethe drive shafts of the pumps 43 and 49. The use of diluent or flushliquid pumped in a closed circuit has two principal advantages over theuse of a bath as in the prior art: in the first place, the pumpeddiluent is under positive pressure and so precludes the entry ofatmospheric air with its charge of moisture; and in the second place,the diluent continuously circulates, thereby continuously to dilute andcarry away the isocyanate that continuously leaks past the ordinary pumpseals and toward the atmosphere.

Such a closed circuit is shown in FIG. 2 in which diluent in atransparent reservoir 93 is pumped through conduit 95 by a small gearpump 97, to the casing 99 that surrounds the drive shaft of gear pump 43(see FIG. 3), and then through the casing 101 that surrounds that driveshaft of a proportioning pump 49 (see FIG. 4).

The system of FIG. 2 is shown as a series system, from pump 43 to pump49. However, it could of course be also a parallel closed system.

Suitable diluents are tricresyl phosphate, mineral oil, dioctylphthalate, and other known diluents. Particularly preferred is tricresylphosphate (TCP), because the TCP that is commercially available tends tocontain less water than the other known diluents. Water is undesirable,because it reacts with the escaping isocyanate to cause the diluent tothicken or gel. Thanks to the fact that the diluent circulates in aclosed system under positive pressure, there will be no intrusion ofwater from the ambient atmosphere; and so the water that is present willbe that which was initially present in the diluent.

There will thus be a progressive build-up of isocyanate in the TCP. Thisbuild-up should not be permitted to proceed beyond a certain proportionof isocyanate in the TCP, say, 10%. TCP and the other diluents areclear, while isocyanate is very dark brown. Hence, the build-up ofisocyanate can be visually monitored, for when the TCP turns brown fromisocyanate, then it is time to change the TCP in reservoir 93. The factthat reservoir 92 is transparent makes possible an easy visual check onthe condition of the TCP.

It has been found that a closed diluent system as shown in FIG. 2 needcontain only about one quart total diluent and need have a flow rate ofonly about 11/2 quarts per minute, at a pressure which need not exceed 6psi gauge.

Referring now in greater detail to FIG. 3, which shows the mounting ofthe drive end of the gear pump 43, it will be seen that pump 43 ismounted on base plate 103 of the machine, the drive shaft 105 of pump 43extending through an opening in base plate 103 and having fixedlysecured to its free end a drive sprocket 107. Casing 99 thus defines anannular chamber 109 that surrounds drive shaft 105 and that is sealedwith the casing of pump 43 and with drive shaft 105. Shaft 105 is sealedand mounted on base plate 103, also with conventional bearings andseals. The diluent thus passes through conduit 95 into and throughchamber 109 and out through conduit 95 on its way to casing 101 ofproportioning pump 49, thereby continuously to bathe the drive shaft 105and to dilute and carry away the isocyanate that inevitably leaks pastshaft 105, and also to exclude moisture from chamber 109 by the positivepressure of the pumped diluent.

Turning now to FIG. 4, the path of the diluent will be seen throughconduit 95 and casing 101, which defines an annular chamber 111 againstthe underside of the casing 113 of pump 49. Chamber 111 surrounds driveshaft 115 of pump 49, which passes through base plate 103 in which itrotates and on which pump 49 is mounted, by means of bearings and sealswhich are entirely conventional and need not be described in greaterdetail. At its free end, shaft 115 has a drive sprocket 117; or shaft115 can be connected to sprocket 117 through a coupling and bearingarrangement as in FIG. 3. Thus, in the case of pump 49, as also in thecase of pump 43, isocyanate that inevitably leaks past the bearings andseals that are provided in ordinary commercial practice for the pump, iscontinuously diluted and carried away by the diluent; and also, again,the positive pressure of the pumped lubricant excludes airbornemoisture.

THE PROPORTIONING PUMPS

As indicated above, the proportioning pumps 29 and 49 are swash platepumps of the type in which a rotary drive shaft rotates a cylinderprovided with a peripheral series of pistons that press slidably againstan inclined swash plate, and whose sliding movement against the swashplate causes the pistons to be advanced into and retracted from thecylinder, thereby to effectuate the pumping action. The pumps 29 and 49of the present invention may be readily available commercial units thathave been modified as described above and that in many ways operateexactly as do other swash plate pumps known to the art. Thus, in commonwith other known swash plate pumps, the drive shaft 115 of pumps 29 and49 rotates in conventional seals and bearings in its casing 113 anddrives in rotation a cylinder 119 that mounts a peripheral series ofpistons 121, that might for example be nine in number, that slide viaslippers 123 on a conventional inclined swash plate 125 that is mountedfor swinging movement in casing 113 about an axis that is perpendicularto the plane of FIG. 4. A coil compression spring 127 urges swash plate125 toward a more steeply inclined position; while a conventionalpressure compensator 129 urges swash plate 125 in the opposite directionupon the attainment of a downstream pressure in excess of apredetermined maximum pressure above working pressure.

Thus, as is conventional, upon attainment of said maximum pressure inpassageway 131, as for example when the gun is closed and there is ano-flow condition but pump 49 continues to operate, piston 133 is forcedto the right, against a spring pressure set by adjustment of nut 135,thereby subjecting chamber 137 to that maximum pressure, whereuponpiston 139 is forced down as shown in FIG. 4, to swing swash plate 125clockwise as seen in FIG. 4 toward a position in which swash plate 125is perpendicular to shaft 115, this latter position being an idle orno-flow position in which the pistons 121 do not move relative tocylinder 119 and so no pumping takes place.

It will of course be understood that the pressure compensator 129 is notthe pressure setting means of the present invention. The pressure of thepump components, that is, the back pressure downstream of pumps 29 and49, is preferably set in the gun head 83 itself. Instead, pressurecompensator 129 operates to move the swash plate toward the idleposition, only at a maximum pressure above the working pressure. Thus,for example, if a working pressure of, say, 800 psi is used, thencompensator 129 might be set to open at, say 1000 psi. The maximumpressure at which compensator 129 is set should be sufficiently highabove the operating pressure that small variations in working pressuredo not trigger swinging movement of swash plate 125, which would alterthe proportion of one component relative to the other and/or stop themachine; at the same time, the maximum pressure should not be greatlyabove the working pressure, because when changing from a no-flow to aflow condition, there would be too great a spurt of liquid when thepressure drops from the maximum pressure that obtains under no flowconditions, to the working pressure that obtains under flow condition.

But in addition to their more conventional aspects, pumps 29 and 49 havea number of features of novelty that enter into patentable combinationin the present invention, as follows:

1. The present invention uses plural swash plate pumps in parallelliquid circuits that ultimately have a common outlet. In this particularcombination, swash plate pumps provide certain advantages never beforeachieved by the gear pumps and reciprocating pumps that have heretoforebeen used in this particular environment. Thus, a swash plate pumpprovides positive displacement and so, when plural swash plate pumps areused, permits positive control of the proportions of the componentsrelative to each other. Moreover, a swash plate pump provides readymeans for relieving over-pressure by swinging to no-flow condition,without necessarily stopping the pump upon no-flow condition. Moreover,the use of plural swash plate pumps in parallel, for the pumping ofparallel streams, enables the ratio of the flow rates of the streams tobe quickly and easily adjusted relative to each other, merely byadjusting the maximum angle to which the swash plate can swing, by meansof conventional adjusting means that are already present on commerciallyavailable swash plate pumps. In this latter regard, swash plate pumpsare superior to gear pumps, in which change of ratio must be effectedeither by the change of speed of one pump, or by the change of gearratio of one pump, either of which adjustments is quite costly toprovide. Swash plate pumps are superior to piston pumps as heretoforeused for the pumping of parallel streams, because piston pumps have apressure cycle which is cyclic per stroke; and so the pressure ratio ofthe two streams tends to vary instantaneously; while by contrast, aswash plate pump, by virtue of its series of pistons, is essentiallyfree from cyclic pressure variation, so that the pressure ratio of thestreams can be maintained essentially constant, not only on the average,but also instantaneously.

2. As will be explained in greater detail hereinafter, exhaustion of thesupply of either component results in a pressure drop below the basepressure of, say, 15 psig, which in turn results in stoppage of themachine, so that the machine will not pump off-ratio. The exhaustion ofone component, however, introduces air into the liquid circuit for theexhausted component. If this air were pumped through upon resumption ofoperation, that is, after replenishment of the exhausted component, thenthe resulting mixture would be off-ratio, and also the pumps would losetheir prime.

Therefore, the swash plate pumps 29 and 49 of the present invention arespecially arranged and their fluid circuits are modified, to purge airfrom the system and to reestablish the integrity of the all-liquidcircuit of what was previously the exhausted component. Thus, uponcomponent replenishment and prior to the resumption of operation, themanually operated valve 33 or 53 is opened, whereby the replenishedcomponent moves through the bypass conduit 31 or 51 into a bypass inlet141 in the bottom of casing 113, and out through a bypass outlet 143 inthe top of casing 113. For this purpose, therefore, casing 113 isarranged upright, so that the axis of drive shaft 115 is vertical andthe intake and exhaust passages (not shown in FIG. 4 as they areconventional) of pumps 29 and 49 are disposed uppermost.

For this purpose, the gun is closed and both of pumps 23 and 29, or 43and 49, are operated with the associated valve 33 or 53 open, whereuponthe liquid moves through bypass conduit 35 or 55 and carries with it thepurged air back to the associated reservoir 1 or 3.

Once the integrity of the all-liquid circuit has been reestablished,then manually operated valve 33 or 53 is closed and on-ratio pumping canresume.

3. As indicated above, it is conventional to provide a manuallyadjustable control for the angle to which the swash plate 125 may swing,thereby to regulate the delivery of the pump. But the present inventionadds a new function, and some new structure, to the function andstructure of this portion of commercially available swash plate pumps.

Such an arrangement can be seen in FIG. 5, which shows the shaft 145 onwhich the swash plate 125 is mounted on casing 113 for oscillatingmovement (vertical swinging movement as seen in FIG. 4) between flow andno-flow conditions. Fixedly secured to shaft 145 is an arm 147 thatextends radially from shaft 145, and that at its free end 149 is adaptedto bear against a rod 151 which is mounted on casing 113 for adjustivemovement in either direction.

Thus far, the structure and function of this portion of the pump 29 or49 as seen in FIG. 5 are conventional. But the present invention addsnew structure and function, by means of an electrical contact 155 thatis mounted on the free end of rod 151 by means of an insulator 157,whereby contact 155 is insulated from rod 151. Contact 155 is in anelectrical circuit whose details will be described hereinafter, througha conductor 159. Casing 113 of pumps 29 and 49 is grounded, so that arm147 is grounded. Thus, an electrical circuit through contact 155 andconductor 159 is respectively established and interrupted, when arm 147swings counterclockwise or clockwise as seen in FIG. 5. As FIG. 5 ispresented, end 149 of arm 147 bears against contact 155 to complete thiscircuit, in the flow condition, and is spaced from contact 155 tointerrupt this circuit, in the no-flow condition. This circuit featureserves, among other things, to control the heating of the pumpedstreams, and the operation of the motor, in a manner that will bedisclosed in greater detail hereinafter.

PUMP DRIVES

As indicated above, there are five pumps 23, 29, 43, 49 and 97,comprising the feed pump 23 for the resin, the proportioning pump 29 forthe resin, the feed pump 43 for the isocyanate, the proportioning pump49 for the isocyanate, and the pump 97 for the diluent. According to thepresent invention, these are all driven by a common drive chain from asingle motor 193 mounted on the upper side of base plate 103. Motor 193drives step-down gearing (not shown), which in turn drives a shaft 161that extends down through base plate 103 and is fixedly secured to adrive sprocket 163. See FIG. 6 of the drawings, which is a bottom planview of the machine of the present invention, that is, from theunderside of base plate 103. Drive sprocket 163, in turn, drives asingle chain 165 that is trained about and drives the sprockets 107 anddrive shafts 105 of the feed pumps 23 and 43, the drive sprockets 117and drive shafts 115 of the proportioning pumps 29 and 49, and the drivesprocket 167 and drive shaft 169 of the diluent pump 97. Spring-urgedtensioning sprockets 171 bear against chain 165 to maintain the propertension therein. Base plate 103 is spaced above and supported on anydesired substrate such as a floor, by means of legs 173 which canterminate downwardly in any desired support, e.g. wheels or casters.

The use of a single drive chain 165 has several advantages. In the firstplace, the chain, which may be any conventional drive sprocket chainwith metal links which may for example be coated or clad withpolytetrafluoroethylene, is inextensible and so it transmits drive toall the components at a precisely predeterminable velocity. In thesecond place, the use of a common drive chain from a single drivesprocket to all of the driven sprockets, insures that all five pumpswill operate in unvarying ratio to each other, whereby the proportionsof the pumped components are maintained constant. In the third place, avery simple drive arrangement is provided which, by virtue of itslocation beneath the base plate, is well protected but at the same timeeasily accessible for maintenance and repair without disassembly of theother parts of the machine that are mounted on the upper side of thebase plate.

HEATING THE PUMPED LIQUIDS

It is often desirable to heat the pumped liquids. For example, when thepumped liquids are mutually reactive, as in the case of resin andisocyanate, then in certain cases the reaction is initiated by heatingthe pumped liquids to a predetermined temperature, e.g. up to 60° C.Broadly, the heating of said pumped liquids is conventional, as are thetemperatures to which they are heated. However, the present inventionprovides new means for heating to those conventional temperatures, andnew controls for achieving and maintaining those temperatures.

The new heating means of the present invention are best seen in FIG. 7;and the new controls are best seen in the circuit diagram whichcollectively comprises FIG. 8.

Referring first to FIG. 7, there is shown partly in section and partlybroken away, the two heated hoses 75 and 77 which were broadly shown inFIG. 1. These hoses have couplings 71 and 73, respectively, at theirupstream ends and couplings 79 and 81, respectively, at their downstreamends, by which they are detachably interconnected to the head 83 of thegun 85. The hoses and their couplings are entirely conventional as thusfar described; and the head 83 of the gun 85 is in no way modified.

The novel structure of the heated hoses, comprises their heating means,in the form of immersed wire coils 175, one disposed in each hose 75 and77. Each coil is secured at opposite ends as by solder or other means ofsecurement at 176 to the adjacent fitting. The hoses 75 and 77 are ofconventional material, e.g. reinforced polytetrafluoroethylene or nylon;but the wire coils 175 are assembled to the fittings prior to assemblyof the fittings on the hoses, so that the heat of soldering does notdamage the hose.

Each coil 175 is helical, and, for example, for a 10 mm. inside diameterhose and an intended thru-put of 5 kg. per minute of liquid, may becopper wire of 1.5 mm. diameter coiled in such a manner that 50 runningmm. of the wire extend over 25 mm. of the length of the hose. The coils175 are free in their respective hoses, and are bonded as by solderingonly at their ends. Thus, the coils within the hoses are free to move toa limited extent within the hoses. Also, the diameter of the coil ispreferably a little smaller than the inside diameter of the hose. Thus,for example, for a hose whose inside diameter is 10 mm. the outsidediameter of the coil might be 8 mm.

The hose heating circuit thus is through the secondary of thetransformer 91, in series through the conductor 89, the coupling 73, thecoil 175 within hose 77, coupling 81, head 83, coupling 79, the coil 175in hose 75, coupling 71, and conductor 87, back to the secondary of thetransformer via certain other circuit elements that will be describedhereinafter. The coils in the two hoses are thus in series with eachother, so that simultaneous operation is insured. Moreover, because theisolation transformer isolates and steps down the voltage to, say, 48 V,it is altogether unobjectionable to have the head 83 of the gun incircuit between the two hose heating coils 175.

It will of course be appreciated that the hoses 67 and 69 are not heatedand no coils pass through them. Therefore, these relatively shortlengths of hose serve as insulation between the electrically conductivecouplings 71 and 73, on the one hand, and the couplings 63, 65 to themachine, on the other hand, thereby insulating the hose heating circuitfrom the machine, but not from the gun head, which latter is in thatcircuit.

It will also be appreciated, with regard to FIG. 7, that the proportionsthere shown are entirely schematic: the hoses could be thicker orthinner; and their lengths will ordinarily be a number of feet, in orderto permit the operator to move the gun over a desirably great distance.Similarly, the hoses themselves will ordinarily be reinforced, in viewof the high pressures involved, in any of a variety of conventionalways.

The hose heating arrangement of the present invention has a number ofadvantages in addition to those recited above. In the first place, it isquite simple to install: as the coil 175 is smaller than the insidediameter of the hose 75 or 77, it is a simple matter to thread a lengthof coil through the hose and to solder its opposite ends to thecouplings just inside the mouths of the couplings.

In the second place, as the hose is heated internally, there is no needfor a primary heater.

In the third place, as mentioned above, the hose coils are in serieswith each other, although it is also possible that they be in parallelor even in separate circuits.

In the fourth place, heating is quick and direct, because the liquidsflow in direct contact with a length of wire about twice the length ofthe hose.

In the fifth place, the coiled configuration of the wire induces acertain amount of turbulence in the flowing liquid, which in turnpromotes heat exchange at the interface between the liquid and thecoils.

In the sixth place, the freedom of the coil to move relative to the hosewithin the hose, insures that even the sharpest or most frequent bendingof the hose will not damage the coil: the hose thus serves to protectthe coil.

Other advantages of the heating system of the pump liquids will becomeapparent from the following description of the circuit diagrams.

ELECTRICAL CONTROLS--LOGIC CIRCUIT

Primary voltage of 220 V AC single phase is supplied to a main circuitbreaker 177, which in turn supplies current to a motor circuit breaker179 and a hose heat transformer circuit breaker 181. Primary voltage isalso supplied to the primary of a transformer 183 whose groundedsecondary supplies current to a logic module 185 whose functions will bedescribed in detail hereinafter.

Hose breaker 181 supplies current through an ammeter 187 to the primaryof the hose transformer 91, whose secondary at 48 V is controlled by thehose circuit board 189 and a triac 191, which, as is conventional in theart, comprises a pair of silicon control rectifiers mounted inanti-parallel with a common gate.

The motor breaker 179 supplies current to the motor relay K2 and to themotor 193.

In logic module 185 there are a number of other relays, namely, a relayK1 which is the 220 V relay; K3 which is the motor stop relay; K4 whichis the relay for the isocyanate proportioner pump 49; K5 which is therelay for the resin proportioner pump 29; K6 which is a conventionaladjustable time delay relay which, in the illustrated embodiment, is setfor three minutes; K7 which is another conventional adjustable timedelay relay which, in the illustrated embodiment, is set for twoseconds; K8 which is the hose heat control relay, and K9 which is theliquid supply relay.

With the machine plugged in, 24 V from the stepdown transformer 183 isapplied to pin 4 of relay 1, to pins 2 and 4 of relay 3, to pin 2 ofrelay 6, to pin 2 of K7 and to pins 2 and 4 of K9. The other side of thesecondary of transformer 183 is applied to chassis ground and each ofK2, K7 and K8 has a grounded contact. On the other hand, K3, K6 and K9are connected to chassis ground indirectly through reset push button195.

The switch illustrated in FIG. 5, which is shown in the closed positioncorresponding to full flow through the associated pump 29 or 49, is aflow mode control switch; and there is one for each of the proportioningpumps 29 and 49. The isocyanate flow control switch is connected toactuate relay K4 while the resin flow control switch is connected toactuate relay K5. When main breaker 177 is on, all relays aredeenergized except for motor control relay K2 which is supplied with 24V from normally closed pin 3 of stop relay K3.

Then when motor control breaker 179 is turned on, the motor 193 startsto run because the motor control relay is energized. At the same time,however, the motor breaker supplies 220 V to the 220 V relay K1 toenergize it. With only the 220 V relay K1 energized, 24 V is appliedfrom pin 3 of K1 to the high and low pressure switches 59, 61, 197 and199, and also to the isocyanate and resin relays K4 and K5. But as thepumps 29 and 49 are stopped, no pressure has been developed. Therefore,the low pressure switches 59 and 61 remain closed and supply 24 V to K9and its pin 1 to energize K9.

With liquid supply relay K9 energized, its pin 3 applies 24 V to stoprelay K3 to energize it. This in turn removes the 24 V from the normallyclosed contact of pin 3 of K3, which supplies 24 V to the motor controlrelay K2. This de-energizes K2, which stops the 220 V at pins 1 and 3 ofK2 to turn off the motor 193.

At this time, K3 is held energized by its own pin 1, which supplies 24 Vto K3, which is grounded through the chassis by reset button 195, aspreviously explained. K1 is de-energized because 220 V is no longerbeing supplied to K2 because it is de-energized.

When normally closed reset button 195 is depressed, that is, opened, itopens the circuit from K3 and K9 to chassis ground, so as to de-energizeboth of K3 and K9. As long as button 195 is held depressed, these relaysremain de-energized which, in turn, energizes K2 to turn on motor 193and activate K1. Ifthe reset pushbutton 195 is released before the feedpumps 23 and 43 come up to pressure above the base pressure of, say, 15psig, relays K3 and K9 will energize again, cutting off the power to themotor 193. Therefore, button 195 must be held depressed until operatingpressures are achieved and low pressure switches 59 and 61 open. If theoutlet pressure to the supply hoses exceeds, say, 1200 psi, then thehigh pressure switches 197 and 199, which are located anywheredownstream of pumps 29 and 49, will open, thus causing K2 to deactivate,which in turn shuts the motor off. This condition continues until theoutlet pressure falls below, say, 1200 psi, whereupon K2 reactivates.

Once the machine is running at normal pressures, and 24 V is applied torelays K4 and K5 to monitor flow conditions and control high heat andlow heat capabilities. With both of pumps 29 and 49 at pressure, in theidle flow mode, K4 and K5 are de-energized. 24 V from pin 3 of K1 isapplied to K5 and its pin 2. With K5 de-energized, normally closed pin 3of K5 applies 24 V to pin 5 of K4. With K4 also de-energized, normallyclosed pin 6 thereof applies 24 V to three-minute timer relay K6 tostart the timer. If nothing changes for three minutes, the timeractivates, giving pin 1 of K4 24 V to apply to stop relay K3 to energizeit which de-energizes relay K2 and turns off the motor.

When K4 and K5 are actuated, that is, when pumps 29 and 49 are pumpingunder full flow conditions, then both of the flow mode switches shown inFIG. 5 will be closed and the corresponding signal lights 201 and 203will be lighted. But when K5 is de-energized, 24 V is removed from itsnormally closed pin 3, which de-actuates K6 via K4, stopping thethree-minute timer. 24 V is now applied to pin 1 of K5, which applies 24V to pin 2 of K4. With K4 also energized, this 24 V is applied to pin 1of K4 and thus sent to pin 2 of K1.

With K1 energized, its pin 1 receives the 24 V and applies it to K8,thereby energizing K8. This puts the heat circuit board 189 in a highheat mode, to be explained in detail later, if hose breaker 181 is on.

But when the pumps 29 and 49 return to the no-flow mode, and theircorresponding flow mode switches shown in FIG. 5 are open, then K4 andK5 are de-energized because chassis ground is no longer supplied bythose flow mode control switches. This de-energizes K8 to return heatcircuit board 189 to a low heat mode, to be explained in detail later,if hose breaker 181 is on. With K4 and K5 de-energized, K6 is energizedand the three-minute timer starts again.

If only one swash plate 125 is fully tilted, then the other pump willdeliver at less than its intended flow rate, and the two streams will beout of proportion relative to each other. This can happen, for example,if the supply runs low in container 1 or 3, or if there is a blockage inone of the conduits, or if for any other reason there is a partial ortotal failure of the supply of one of the liquids. Under thesecircumstances, only one of the flow mode control switches as shown inFIG. 5 will be closed, that is, activated. If it is, for example, theresin control switch which alone is activated, then only the resinrelay, K5, will be energized. This removes 24 V from the normally closedpin 3 of K5 to stop the threeminute timer but closes the normally openpin 1 of K5 to send 24 V to pin 2 of the isocyanate relay K4. With K4de-energized, 24 V is placed on its normally closed contact pin 3,whence it actuates K7. If this condition exists for more than twoseconds, K7 energizes, sending 24 V from its pin 2, to pin 3 of K3,which energizes K3 to stop the motor 193.

But if the resin flow mode control switch deactivates before twoseconds, then K5 de-energizes and stops the two-second timer and goesback to the no-flow condition and starts the three-minute timer again.If the isocyanate flow mode control switch activates before the twoseconds has expired, and the resin flow mode continues, then both K4 andK5 energize. This removes 24 V from the two-second timer and applies itto K1 to go into the high heat mode, by energizing K8, which is thenormal flow condition.

But if the isocyanate flow mode control switch alone is activated, thenthe corresponding relay K4 alone is energized. In this manner, the resinrelay, K5, supplies 24 V from its pin 3 to pin 5 of K4. With K4energized, 24 V is applied to pin 4 of K4, and thence to two-secondrelay K7 to energize it. As in the case of K5, so also in the case ofK4, if K4 is de-energized before two seconds, the circuit goes back tothe normal no-flow condition, but if K5 is energized, then normal flowconditions prevail and neither timer runs.

Normal flow conditions thus can prevail without any time limit, so longas trigger valve 86 is pressed. Air under control of a conventional airsolenoid 207 is thus supplied to the conventional piston that retractsthe conventional valve rod in the conventional gun 85 to effectdispensing.

In addition, a microswitch (not shown) can be provided within gun 85,operated by the rearward movement of the air piston to shut down themachine with a two-second delay when both pumps 29 and 49 are out ofproportion at the same time while dispensing is taking place.

ELECTRICAL CONTROLS--HOSE HEAT CIRCUIT

Passing reference was made above to the high heat and low heat modes ofthe hose heat circuit, which is indicated in the drawings by the hoseheat module 189 with its associated relay K8. This refers to the factthat according to the high heat mode, a substantially greater quantityof heat is applied by electric resistance heating to the liquids whenthey are flowing through the conduits 75 and 77, than when they are notflowing. The former case is the high heat mode and the latter case isthe low heat mode. For example, 48 V can be applied at a current ofabout 60 amperes during high heat mode and the same voltage at a currentof about 10 amperes during low heat mode. Broadly speaking, high heatmode occurs only when both pump stops are on their contacts as seen inFIG. 5, and motor 193 is running, and heat circuit breaker 181 is on.But low heat mode is independent of motor operation and occurs when thehose breaker 181 is manually actuated, for example for warm-up prior tomotor operation. Also, when motor 193 cuts out, the low heat modecontinues. Furthermore, the de-activation of either one of relays K4 andK5 will switch the circuit from high heat to low heat.

Thus, when hose breaker 181 is turned on, 220 V is applied totransformer 91, the 48 V secondary of which is connected directly to oneside of the heated supply hoses, the other side of the 48 volt secondaryof transformer 91 being connected through triac 191 to the other side ofthe heated hoses, whereby triac 191 controls the amount of current at 48V which flows through the supply hoses, that is, high current at highheat mode and low current at low heat mode. Triac 191 is controlled bycircuitry adjusted for high and low current flow, as determined by thepins 1, 2 and 3 of heat control relay K8. Normally closed pin 3 of K8maintains the low current setting. But when K8 is energized by K1, thennormally open pin 1 of K1 applies gate for the high heat mode.

Referring now in greater detail to the circuit diagram associated withthe heat control module 189, it will be appreciated that adjustment ofeach of the heat control modes is effected through R11 and R12, whichthus form the controlling portion of the gating or switching networkthat allows triac 191 to conduct in its two states, high or low. Triac191, in turn, can best be described as a fast switching device. Thelonger the triac is switched on during a single cycle of the 50 or 60hertz power source, the more current is allowed to flow from the hoseelement through the triac and back to the power source, for electricresistance heating of the liquids in the hoses. Conversely, the lesstime the triac is switched on, the less current is allowed to flowthrough the hose heater coils.

The rest of the gating network that connects to R11 and R12 is a simpleresistance-capacitance timing circuit that forms a pulse of energy thatis discharged through diac 205, which is a bi-directional diode that canconduct power in either direction (negative or positive). This enablestriac 191 to conduct during both halves of the 50 or 60 hertz cycle. R6,R7 and R8 are range-limiting resistors for the low heat state, whichlimit the amount of possible conduction of triac 191 during that lowstate. In FIG. 8, R6, R7 and R8 are labelled 208, 220 and 240,respectively, which means that it is thus possible to control the rangelimiting the low heat state at various line voltages. The output of diac205 connects to the gate of triac 191. C10 and R10 thus form a dV/dTnetwork, (dV/dT being the differential of rate of change of voltage withtime) that protects the triac from any inductive transient power surgesduring turn-on or turn-off. Thus this network serves in effect as aninductive shock absorber.

During the low heat mode, the gating signal passed to triac 191 is fromR3 through either R6, R7 or R8, and through the adjustable rheostat R12.Once the signal level is past R12, the pulse-shaping network (C 7-8, R5,C6) develops the gating pulse. The gating pulse now travels to pin 3 ofK8. The pulse passes through pin 2 of K8 and returns to module 189 todiac 205. The pulse now conducts through diac 205 and forces triac 191to conduct.

But during the high heat mode, the gating signal path is through R4 andadjustable rheostat R11. The signal level now enters the gate pulseshaping network (C 3-5, R9, C9) and exits through pin 1 of K8. Due tothe fact that a high heat mode exists, the gate pulse is allowed to passthrough pin 2 of K8 and continue to diac 205. Triac 191 now conducts inthe high heat mode.

From a consideration of the foregoing disclosure, therefore, it will beevident that all of the initially recited objects of the presentinvention have been achieved.

Although the present invention has been described and illustrated inconnection with preferred embodiments, it is to be understood thatmodifications and variations may be resorted to without departing fromthe spirit aof this invention, as those skilled in this art will readilyunderstand. Such modifications and variations are considered to bewithin the purview and scope of the present invention as defined by theappended claims.

What is claimed is:
 1. A feeder for apparatus for ejecting urethane foamformed by the mixture of resin and isocyanate, the feeder comprising aunitary assembly of means for pumping resin and means for pumpingisocyanate toward said apparatus, said isocyanate pumping meanscomprising at least one rotary pump having a rotary drive shaft, andmeans for bathing said drive shaft in tricresyl phosphate thatcirculates in a closed circuit in a closed system under positivepressure thereby continuously to dilute and flush away isocyanate thatleaks along said rotary drive shaft.
 2. A feeder as claimed in claim 1,said bathing means including a transparent reservoir for said flushingliquid by which the condition of said flushing liquid may be visuallymonitored.